John Calvin (1509-64 AD)
“There are three than bear record in heaven The whole of this verse has been by some omitted. Jerome thinks that this has happened through design rather than through mistake, and that indeed only on the part of the Latins. But as even the Greek copies do not agree, I dare not assert any thing on the subject. Since, however, the passage flows better when this clause is added, and as I see that it is found in the best and most approved copies, I am inclined to receive it as the true reading.”
Source: Calvin’s Commentaries, 1 John 5:7